The Chromatic Index of Proper Circular-arc Graphs of Odd Maximum Degree which are Chordal. Bernardi, J. P. W., da Silva, M. V. G., Guedes, A. L. P., & Zatesko, L. M. Electronic Notes in Theoretical Computer Science, 346:125-133, 2019. The proceedings of Lagos 2019, the tenth Latin and American Algorithms, Graphs and Optimization Symposium (LAGOS 2019)
The Chromatic Index of Proper Circular-arc Graphs of Odd Maximum Degree which are Chordal [link]Paper  doi  abstract   bibtex   
The complexity of the edge-coloring problem when restricted to chordal graphs, listed in the famous D. Johnson's NP-completeness column of 1985, is still undetermined. A conjecture of Figueiredo, Meidanis, and Mello, open since the late 1990s, states that all chordal graphs of odd maximum degree Δ have chromatic index equal to Δ. This conjecture has already been proved for proper interval graphs (a subclass of proper circular-arc ∩ chordal graphs) of odd Δ by a technique called pullback. Using a new technique called multi-pullback, we show that this conjecture holds for all proper circular-arc ∩ chordal graphs of odd Δ. We also believe that this technique can be used for further results on edge-coloring other graph classes.
@Article{Bernardi2019,
   title        = {The Chromatic Index  of Proper Circular-arc Graphs of
                  Odd Maximum Degree which are Chordal},
   journal      = {Electronic Notes in Theoretical Computer Science},
   volume       = {346},
   pages        = {125-133},
   year         = {2019},
   note         =  {The proceedings of  Lagos 2019, the tenth  Latin and
                  American Algorithms, Graphs and Optimization Symposium
                  (LAGOS 2019)},
   _keywords    = {Universal2016},
   organization = {UFMG},
   issn         = {1571-0661},
   doi          = {https://doi.org/10.1016/j.entcs.2019.08.012},
   url                                                                 =
                  {http://www.sciencedirect.com/science/article/pii/S1571066119300623},
   author       = {João Pedro W. Bernardi and Murilo V. G.  da Silva and
                  André Luiz P. Guedes and Leandro M. Zatesko},
   keywords        =   {Pullback,    circular-arc,   chromatic    index,
                  edge-coloring, chordal},
   abstract      = {The  complexity  of the  edge-coloring problem  when
                  restricted  to chordal  graphs, listed  in the  famous
                  D. Johnson's NP-completeness column  of 1985, is still
                  undetermined.  A  conjecture of  Figueiredo, Meidanis,
                  and Mello, open since the  late 1990s, states that all
                  chordal graphs of odd  maximum degree Δ have chromatic
                  index  equal to  Δ. This  conjecture has  already been
                  proved  for  proper  interval graphs  (a  subclass  of
                  proper circular-arc  ∩ chordal graphs)  of odd Δ  by a
                  technique  called  pullback.   Using a  new  technique
                  called  multi-pullback, we  show that  this conjecture
                  holds for all proper  circular-arc ∩ chordal graphs of
                  odd Δ. We also believe that this technique can be used
                  for  further  results  on  edge-coloring  other  graph
                  classes.}
}

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